1. Field
Embodiments of the invention relate to the field of light emitting diodes (LEDs), and more particularly to LEDs fabricated to reduce the dispersion of emitted light.
2. Background
In light emitting diodes (LEDs), light is produced by a solid state process called electroluminescence. LEDs are becoming increasingly efficient. The efficiency is increasing (lumen/watt) due to improved thermal efficiency and the use of blue LEDs with a high efficiency that are combined with color converting phosphors. Light extraction in LEDs involves the set of particular problems that is connected with getting light from the light emitting p-n junction in a LED to the surroundings, such that the light might be useful, for instance for lighting.
Unfortunately, LEDs emit light not is not directional. The emissive surface of an LED is small, but the light rays are emitted from the emissive part an approximately half sphere, Lambertian radiation pattern. For many applications, a light source is needed with a smaller angular spread. To increase the extraction efficiency and to shape the light output provided by an LED, optics such as lenses and/or reflectors may be used to redirect the light rays emitted by the LED to the needed direction.
Additional optics to shape the LED's light output may be bulky. Further, a significant amount of the light output may be difficult for the additional optics to collect and direct because of the direction in which it is emitted from the LED. It would be desirable to provide a light guide that can be closely coupled to an LED so the LED emits light rays more directionally.